妹のために魔法少女になりました

In this world, there are heroes and magical girls who make contracts with spirits to defeat creatures called Phantoms, which feed off negative human energy. The protagonist, Kisaragi Kurona, is one such individual who fights Phantoms. However, the power he possesses doesn’t manifest as a hero, something most boys would admire. So, what does it manifest as? Shockingly, Kurona transforms into a magical girl, which is the complete opposite of both his gender and the typical dreams of young boys. The sole reason Kurona chose to be a magical girl is simple: his sister loved magical girls.